The present invention relates to optical devices having optical waveguides which are widely used in optical communication and optical measurement, a connecting method for the optical devices and a manufacturing method thereof. Particularly, the present invention relates to a waveguide type optical device with optical receptacles which are connected to and fixed at optical waveguides. The waveguide type optical device is constructed in a manner such that an optical fiber outside of the device and the optical waveguide may be connected optically through the medium of an optical fiber located within the hole of the optical receptacle fixed at the optical waveguide. More particularly, the present invention relates to a waveguide type optical device with optical receptacles which is constructed in a manner such that, when connecting the outside optical connector with the optical receptacle, the end face of the ferrule of the optical fiber with ferrule, located within, or inserted into, the hole of the optical receptacle may contact with the end face of the optical connector ferrule of the outside optical connector.
Due to the recent rapid progress of the optical communication technology, various optical devices using optical waveguides such as optical couplers (hereinafter referred to as "waveguide type optical devices") have been developed and such devices are widely used and praised in optical fiber networks related to optical communication and optical measurement. Installment of optical waveguides as components of optical devices allows for the development of the optical devices on which plural functions are accumulated. Waveguide type optical devices are attracting public attention as optical devices which enable efficient mutual coupling of plural optical fiber networks.
According to the differences in the construction of optical device products, there are two main types: the pig tail type, an optical device with which an optical fiber is connected, and the optical receptacle type, an optical device on which optical receptacles are installed. In the pig tail type, the optical device may be coupled to an optical fiber network by causing fusion splicing between the optical fiber of the optical fiber network and the optical fiber of the optical device connected to the optical fiber network, or by furnishing optical connectors at the end portion of the optical fiber of the optical fiber network and at the end portion of the optical fiber of the optical device and connecting these optical connectors, for example, through an optical adapter. On the other hand, with the optical receptacle type, the optical fiber of the optical fiber network and the optical waveguide of the optical device may be easily connected by engaging the optical connector, which is installed at the end portion of the optical fiber of the optical fiber network, with the optical receptacle of the optical device.
The optical device of the pig tail type needs two optical connectors, one on the optical device, one on the optical fiber network, and one optical adapter or optical receptacle to connect these optical connectors. The optical device of the optical receptacle type, however, does not need any optical connector on the optical device side. Therefore, by applying the optical device of the optical receptacle type, the number of optical components for connection with the optical fiber network, such as optical connectors, optical adapters, and/or optical receptacles, may be decreased and, furthermore, the complicated connecting work at the work place may be greatly reduced or even eliminated. Accordingly, if we could easily manufacture waveguide type optical devices with optical receptacles at a low cost, we may expect that the optical devices will be readily incorporated into the optical networks, making use of the characteristics of the optical waveguides, and that it will become possible to construct optical networks at a low cost, thereby contributing in a definite way to the rapid progress of the optical communication technology and the development and advancement of the international information industry.
It is known that if a space, i.e., gas phase, already exists between the optical fiber and the optical waveguide connected thereto, the coupling loss increases due to reflection and scattering. The easiest method to connect the optical fiber and the optical waveguide without making a space between the optical fiber and the optical waveguide is to cause the end portion of the optical connector of the optical fiber network to directly contact with the optical waveguide of the optical device. However, this method or construction will flaw on the end face of the optical waveguide when the outside optical connector is attached or removed. Once the end face of the optical waveguide is flawed, such flaw will cause the reflection or scattering of signal light and the optical transmission performance will deteriorate. Particularly, if polymer optical waveguides are applied as the optical waveguide, the optical transmission performance will be affected greatly.
In order to prevent and avoid damage to the end face of the optical waveguide upon removal or attachment of the optical connectors, we may insert an optically transparent material which is highly resistant against mechanical friction, such as a thin plate glass, between the optical waveguide and the optical connector. However, it is necessary to carefully select the material of the plate glass to be inserted between the outside optical fiber and the optical waveguide, and to make the thickness of the plate glass extremely thin. Practically, it is not easy to manufacture an extremely thin material such as plate glass and, moreover, it will become expensive.
The objective of the present invention is to facilitate the construction of optical networks at a low cost by offering inexpensive waveguide type optical devices with optical receptacles and to contribute in a definite way to the rapid progress of the optical communication technology and the development and advancement of the international information industry.
Another objective of the present invention is to reduce the coupling loss between the outside optical fiber system and the optical waveguide of the waveguide type optical device as much as possible.
A further objective of the present invention is to offer a construction which will prevent the end portion of the optical waveguide of the optical device from suffering flaws by the repeated insertion of the optical connector of the outside optical fiber into the optical receptacle of the optical device.
Another further objective of the present invention is to offer a method of connecting the optical device with the outside optical fiber network and a method of manufacturing the optical device.